中文摘要：

针对传统的三维频率域可控源电磁法有限元数值模拟数据量大、耗费时间长的问题，引入无限单元来取代施加在外边界上的人工边界条件。电磁场在无限单元内扩散至无限远处，并最终衰减为0。由此，有限元剖分区域的范围被大幅减小，总自由度数相应降低，计算速度随之加快。数值模拟结果表明：采用本文提出的有限元-无限远结合算法后，有限元网格化区域不到原先的1%，自由度总数减少约33%，求解时间节省约25%，计算精度与大范围下施加Dirichlet外边界条件的有限元结果相当。

英文摘要：

Due to the large scale of the survey domain, the three dimensional （3D） controlled source electromagnetic （CSEM） numerical modeling usually brings about large amount of data and is very time consuming. To solve these problems, in this study, infinite elements were introduced into the finite element analysis to substitute the conventional artificial boundary conditions, which made the electromagnetic fields diffuse to infinity and attenuate to 0. As a result, the discretization domain for finite elements, as well as the total number of degrees of freedoms and time consumption, can be reduced remarkably. The numerical tests show that with the finite-infinite element coupling algorithm, the finite elements discretization domain is less than 1% of the conventional finite element modeling. The total numbers of freedom degrees are reduced around 33%, and time consumptions are saved around 25% while the accuracy is equal.